1. Field of the Invention
The present invention relates to a recording apparatus and, more particularly, to a recording apparatus and its peripheral circuits, the apparatus accommodating temporarily the print data to be supplied to a print head.
2. Description of the Prior Art
Diverse kinds of serial recording apparatuses have been developed so far and are used extensively. These apparatuses include dot impact type, thermal type and ink jet type printing apparatuses. In particular, ink jet printers of higher resolution and higher speeds than ever before continue to be developed; they are expected to find their way into an ever-growing range of applications.
In general, the serial recording apparatus has a recording head mounted on a carriage, the recording head printing a single column of data perpendicular to the scanning direction of the carriage. With the carriage making a scanning motion, a predetermined width of a band-shaped area is printed. After each scan of the carriage, a transport roller assembly transports a recording medium by a predetermined amount. The operations are repeated to complete printing on each sheet of recording paper.
FIG. 18 is a schematic plan view of a recorder included in a typical serial recording apparatus. In FIG. 18, reference numeral 101 is a recording head; 102 is a carriage; and 103 is a recording medium. The recording head 101 prints vertically from top to bottom, the carriage 102 scans crosswise, and the recording medium 103 is fed from bottom to top. The direction of printing by a nozzle array of the recording head 101 (i.e., vertical direction) will be called a vector direction hereunder.
The above serial recording apparatus, if constructed illustratively as an ink jet printer, is best suited for printing not only characters but also images because of its high resolution capability. For that reason, more and more ink jet printers are adopted in the printing and recording assemblies of copiers, facsimile machines and other related recording apparatuses.
FIG. 19 is a schematic plan view of a reader included in a typical image reading apparatus. In FIG. 19, reference numeral 111 is a scanner and 112 is an original. As illustrated in FIG. 19, the image reader in copiers or facsimile machines uses as its scanner 111 a line sensor as wide as the original 112 to be read. With the original 112 scanned crosswise by the line sensor one line at a time, the original 112 or the scanner 111 is fed vertically. This allows image data to be read from the original 112. The reading direction of the scanner 111 (i.e., crosswise direction) will be called a raster direction hereunder.
Suppose that the image data obtained in the raster direction by the above-mentioned typical image reading apparatus are to be printed by the typical recording apparatus above which prints in the vector direction. In that case, the difference between the direction in which the image data were read and the direction in which they are to be printed requires a special arrangement to be provided. That is, the image data to be printed upon a single carriage scan in the raster direction are initially stored temporarily, and the stored data are read in the vector direction in such a manner that they will comply with the direction of the nozzle array. In other words, the image data in the raster direction need to be converted in format to those in the vector direction.
Prior art ink jet printers use a page memory to accomplish the format conversion. Image data in the raster direction are placed temporarily in the page memory and are read therefrom for the conversion by software. The conversion process takes time and lowers the processing speed of the entire system. One solution to this problem is disclosed in Japanese Patent Laid-Open No. SHO/58-195357, SHO/58-195358 and SHO/58-195359. The disclosed techniques involve a bit pattern storage device with a capacity of N.times.L.times.P (bits), where N stands for the number of nozzles, L for the print width and P for the number of nozzles per millimeter. Data are read into the storage device sequentially, in units of words in the raster direction. From the storage device, the data are read in the vector direction by the number of words corresponding to the nozzle count at a time. The read data are held in registers from which appropriate bits are selected to form single-column print data in the vector direction.
The storage device proposed in connection with the above prior art techniques allows one word (e.g., 16 bits) to be accessed per address. Generally, it is convenient for computer-based processing to utilize a storage device that may be accessed in units of words. According to the above prior art, reading print data word by word from the storage device requires setting up as many registers as the number of nozzles involved. If 128 nozzles exist and the internal data length is 16 bits, there will be needed 128 registers of 16 bits long each. This entails bloated print data reading control circuits leading to an enlarged apparatus and higher manufacturing costs.
In addition to image data, text data are also fed to the recording apparatus. Characters included in the text data are converted to the font data contained in a font storage device. On many printing apparatuses, the font data are sent unmodified to the recording head for recording, and normally there is little problem involved in this respect. Sometimes, it may be desired to print data on a sheet wider than the standard B4 size for which the recording apparatus is designed. In such a case, the print image is rotated 90 degrees for printing onto the B4 recording medium that is transported vertically. This, too, involves format conversion regarding the font data.
A set of techniques for rotating print images by 90 degrees for printing is disclosed illustratively in Japanese Patent Laid-Open No. SHO/58-195365. The disclosed techniques involve furnishing a page memory in which the print data fed in the raster direction are written in units of words in the vector direction. From the page memory, the print data are read sequentially by the number of words corresponding to the nozzle count at a time, the read data being subjected to format conversion. In that case, if the data are to be printed in the normal direction, the data need to be converted from the raster-direction, word-based format to vector-direction, word-based format before being stored into the page memory. Otherwise the data cannot be written to the page memory. That conversion process also takes time. If font data are to be developed within the page memory, additional steps are needed to make the word boundaries of the font data and page memory coincide with one another. Such additional processing overhead further reduces the speed of processing.